How the AP-NORC Center survey was conducted

The Associated Press-NORC Center for Public Affairs Research poll on health insurance coverage and costs was conducted from July 22 to September 3 by NORC at the University of Chicago. The survey was funded by the Robert Wood Johnson Foundation.

It is based on landline and cellular telephone interviews with a nationally representative random sample of 1,004 privately insured adults age 18 to 64. Interviews included 602 respondents on landline telephones and 402 on cellphones.

Digits in the phone numbers dialed were generated randomly to reach households with unlisted and listed landline and cellphone numbers.

Interviews were conducted in both English and Spanish.

As is done routinely in surveys, results were weighted, or adjusted, to ensure that responses accurately reflect the population's makeup by factors such as age, sex, education, race/ethnicity and region. In addition, the weighting took into account patterns of phone use — landline only, cellphone only and both.

No more than 1 time in 20 should chance variations in the sample cause the results to vary by more than plus or minus 4.1 percentage points from the answers that would be obtained if all adults in the U.S. were polled. The margin of sampling error is larger for subgroups.

There are other sources of potential error in polls, including the wording and order of questions.